This invention relates to the general field of radiating energy devices, and more particularly to a device that radiates energy to shrink a thin film.
Presently in the fast food drink industry it is typical to serve a drink in a paper, plastic or other disposable cup topped with a preformed plastic lid. However, there are a number of problems associated with the use of these plastic lids including high cost, a bulky size leading to difficulties in storage and disposal, leakage, and non-hygienic handling. In order to overcome these problems various devices and methods have been proposed in which a cover is placed on an open-topped container and then heated to shrink it into sealing engagement with the top of such a container.
One approach is provided in U.S. Pat. No. 5,511,360 to Bakker. This patent teaches a housing to receive and position the disposable cup. A thin film cut in a generally circular shape is urged across the open top of the cup, with an edge portion draping over the periphery. A first radiant energy source directs radiant energy to this overhanging portion. There is an energy absorbing means to absorb the energy and communicate it to the overhanging portion, causing it to shrink and form a seal around the periphery of the open top of the cup. Subsequently a second radiant heater shrinks the top portion of the thin film, completing the seal.
The first radiant energy source taught in the patent comprises two or more heaters, preferably tungsten halogen lamps, that are mounted on pivot arms and connected by slip rings and other complicated mechanical links back to a drive belt and a dedicated motor. Each lamp is only capable of directing energy towards a small portion of the film. Accordingly, the lamps must be rotated about the open top to ensure a complete seal. Application of the first radiant energy therefore involves positioning the lamps closely adjacent to the draped over edge of the thin film, activating the motor to rotate the lamps, and activating the lamps themselves to emit heat energy.
While this method effectively delivers the radiant energy, it requires many extra components and involves many moving parts, adding to the expense and complexity of the equipment. Further, since only a portion of the shrink film is exposed by the rotating lamps at any given moment of the process, the lamps need time to expose the full periphery of the container. In the xe2x80x9cfast foodxe2x80x9d industry, time in seconds or even fractions of seconds are important. Thus the extra time required to rotate the lamps, as well as the cost and complexity of the equipment needed to support and operate the lamps is a disadvantage.
What is required is a radiant energy device for shrinking a thin film which overcomes the problems associated with the current devices.
Most particularly, the device should be relatively simple and uncomplicated, and preferably have only a few or no moving parts to minimize overall cost and maintenance requirements. The device should perform the task of shrinking the thin film and completing the seal as quickly as possible to accommodate the productivity demands of the food service industry.
The device of the present invention accomplishes these ends by arranging a lamp or lamps in a fixed position about the open top of the container, rather than by rotating them in space. In one embodiment an array of single lamps are positioned around the periphery of the open top end of the container. A switching means is included to energize the lamps in a patterned sequence to reduce peak energy consumption. In another embodiment a single lamp combined with a directing means is used to direct the radiant energy from a fixed position.
Accordingly, there is provided a radiant energy device for shrinking a thin film onto an open top of a container, said radiant energy device comprising:
(a) a source of power, to provide power to said radiant energy device;
(b) a plurality of fixed energy-emitting units, each of said units when energized being configured to emit radiant energy towards said shrinking film on said open top of said container; and
(c) a switching means, operatively connected between said source of power and each of said energy-emitting units, to independently activate at least two groups of said energy-emitting units;
wherein, a first group of said energy-emitting units partially shrinks said thin film onto said container, and a second group finishes said shrinking.
In a further embodiment there is also provided a radiant energy device for shrinking a thin film onto an open top of a container, said radiant energy device comprising:
(a) a source of power, to provide power to said radiant energy device;
(b) an energy-emitting body, said body emitting radiant energy upon being energized by said source of power; and
(c) a directing means defining an opening, said directing means being sized and shaped to direct said emitted radiant energy continuously about a periphery of said opening;
wherein, upon said energy-emitting body being energized, said directed radiant energy shrinks said thin film to cover said open top of said container.
In a further embodiment there is also provided a radiant energy device for activating a shrinking thin film to cover an open top of a container, comprising:
(a) a variable source of power, to provide power to said radiant energy source;
(b) a plurality of energy-emitting units, each of said units being configured to emit enough radiant energy towards said open top of said container at a high power level to cause said film to shrink, and to emit a low enough amount of radiant energy at a low power level to not cause said film to shrink; and
(c) a switching means, operatively connected between said source of power and each of said energy-emitting units, to switch said source of power between said high power level and said lower power level;
wherein, upon switching from said low power level to said high power level causes less of a power surge than switching said power level from off to said high level.